Solenoid gas valve

ABSTRACT

A solenoid valve has a main body defining a gas inlet passage, a gas outlet passage, and a cavity; a core tube forming a closure for said cavity so as to prevent an escape of gas; a cylindrical main piston slidably movable in said cavity of said main body, said main piston forming a front chamber and a back chamber in said main body, said main piston having a gas conduit for passing the gas from said gas inlet passage to said front chamber and an axial hole for passing the gas from said back chamber into said gas outlet passage with a bleed orifice at one end of said axial hole; said main piston being spring biased to a closed position; a spring biased pilot piston; and electrical coil means associated with said core tube to provide a magnetic field for movements of said pilot piston and said main piston, so that when said coil means is deenergized said pilot piston closes said outlet passage and causes a pressure equalization allowing said return spring to push said main piston to close the valve, while when said coil means is energized said pilot valve opens said outlet passage and lowers a pressure which causes pushing of said main piston to open the valve.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to solenoid gas valves, and more particularly to a dual active pistons solenoid gas valve, in particular for alternative fuels vehicles.

[0002] In vehicles that run on gaseous alternative fuels, such as natural gas or hydrogen, the fuel is normally stored in a high-pressure tank, and a valve is utilized to open and close access to conduits, along which such high-pressure gaseous fluids flow from a storage tank to a vehicle engine. Typically such valves are of the solenoid type.

[0003] Solenoids of a reasonable size can typically produce a pulling force that is approximately only {fraction (1/100)} of the force necessary to unseat a valve that is being forced shut by the high-pressure gasses. To overcome this, most of the gas valves adapt a two-stage process in which a small “bleed” orifice is first opened, allowing the high-pressure gas from the storage tank to flow through the “bleed” orifice and into a downstream outlet passage way that leads the engine. As the downstream outlet passage way fills up with gas, the pressure will increase, subsequently gradually reducing the force necessary to unseat the closed valve. Eventually, the differential pressure between the upstream and downstream passage ways becomes so small as to allow the valve to be open by the relatively weak pull of the solenoid valve, thus resulting in the flow of high-pressure gas from the storage tank to the vehicle engine.

[0004] One of the main problems with the above described system is the length of time required for the downstream chamber to fill with a sufficient volume of high-pressure gas, so that the solenoid can unseat the main valve. This problem is exasperated in large vehicles, such as buses where the gaseous fuel storage tank can be several meters away from the engine and therefore, it may take an unacceptable period of time for the passageway downstream of the valve to fill up to the point when the solenoid can unseat the main valve. These valves are also disadvantageous in vehicles that are bi-fueled by gasoline and natural gas or dual-fueled by diesel fuel and natural gas. When these vehicles switch over from liquid fuel to natural gas, there can be a conspicuous loss in power output over an unacceptable period of time, while the passage way downstream of the valve fills up with natural gas.

SUMMARY OF THE INVENTION

[0005] Accordingly, it is an object of the present invention to provide a solenoid gas valve of the above mentioned general type which avoids the disadvantages of the prior art.

[0006] It is also an object of the present invention to provide a solenoid gas valve which has an intrinsic ability to shut off gas flow when a battery voltage is diminishing, so that when the battery becomes weaker, the pull on the pilot piston will weaken accordingly allowing it to close, so as to provide equalization of pressures in two chambers and sealing of the main piston, to stop the flow of gaseous fuels to the engine when the battery expires and the vehicle stops running.

[0007] It is also another object of the present invention to provide a solenoid gas valve that will virtually open and close instantaneously, once the solenoid coil is energized, so that a very rapid and immediate opening of the valve to a wide-open position is performed.

[0008] It is also another object of the present invention to provide a solenoid gas valve in which there is no reliance on the built-up pressure within a downstream outlet passage way as a means for operating the valve, so that the inventive solenoid gas valve can operate soundly and rapidly independently from the pressure in the downstream outer passage way.

[0009] In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a solenoid gas valve which has a main body defining a gas inlet passage, a gas outlet passage, and a cavity; a core tube forming a closure for said cavity so as to prevent an escape of gas; a cylindrical main piston slidably movable in said cavity of said main body, said main piston forming a front chamber and a back chamber in said main body, said main piston having a gas conduit for passing the gas from said gas inlet passage to said front chamber and an axial hole for passing the gas from said back chamber into said gas outlet passage with a bleed orifice at one end of said axial hole; said main piston being spring biased to a closed position; a spring biased pilot piston; and electrical coil means associated with said core tube to provide a magnetic field for movements of said pilot piston and said main piston, so that when said coil means is deenergized said pilot piston closes said outlet passage and causes a pressure equalization allowing said return piston to push said main piston to close the valve, while when said coil means is energized said pilot valve opens said outlet passage and lowers a pressure which causes pushing of said main piston to open the valve.

[0010] When the solenoid gas valve is designed in accordance with the present invention, it avoids the disadvantages of the prior art and provides for the above-specified advantages.

[0011] The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an axial sectional view through a valve in accordance with the present invention, in a closed condition;

[0013]FIG. 2 is an axial sectional view through a core-tube of the valve in accordance with the present invention;

[0014]FIG. 3 is a view substantially similar to the view of FIG. 2, but showing the inventive valve when a solenoid coil is not energized;

[0015]FIG. 4 is an axial sectional view of the inventive valve when solenoid coil has been energized; and

[0016]FIG. 5 is a view showing the inventive valve when a main piston is open.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A rapid action solenoid gas valve in accordance with the present invention is illustrated in FIGS. 1 through 5. FIGS. 1 and 2 describe parts that make up the solenoid gas valve. The coil 1 and yoke 2 are mounted on a core-tube with a screw 3. The core-tube includes of a stop 4, a sleeve 5, and a flange 6. The magnetic circuit is formed by the guide sleeve 26 and the molded pilot piston 9, both of which are constructed from ferromagnetic material. The core-tube assembly, including the coil and yoke, is threaded into the cavity 51 of the main body. An O-ring 7 is provided at the junction of the core-tube assembly and the main body 50. The main body 50 is connected to an inlet chamber 16, which fills the front chamber 25 with high-pressure gaseous fuel via an orifice 28 connected to an opening 29 in the spacer 21. The long drill hole 23 connects the valve outlet to an opening leading to a downstream passageway 24.

[0018] A main piston 19 controls the main gas stream by sliding up and down within a sleeve 13. The valve shuts off when the main piston 19 slides down against the seal 20, and opens when the main piston 19 slides away from the seal 20. An O-ring 22 is provided underneath the seal in order to prevent gas leakage. A threaded nut 14 holds the spacer 21 and seal 20 in place. An insert 18 is pressed into a counter hole of the main piston to allow high-pressure gas flow into the back chamber. An appropriate sealant is placed around the insert 18 to avoid gas leakage into the interstitial spaces between the main piston 19 and the front chamber 25. The core tube also contains a seal 12 that prevents gas leakage between these interstitial spaces. High-pressure gas flows from the front chambers 25 to the back chamber 15 via a network of spaces, orifices and passageways (36, 30, 31, 32 and 33). The minuscule inlet hole 30 limits the high-pressure gas flow when the valve is opened and that helps create the pressure difference between the two chambers. An O-ring 17 is placed into a machined groove of the main piston in order to prevent gas flow between the two chambers via the interstitial spaces between the main piston 19 and the spacer 13.

[0019] When the coil 1 is energized, the pilot piston 9 opens and high-pressure gas from the back chamber 15 bleeds out of the valve through another network of orifices and passageways (35, 27, 23 and 24). A drain orifice 35 and a relatively long passageway 27 are drilled intro the main piston 19, and they lead to the valve outlet. A return spring 11 inside the core-tube applies a force against the main piston 19 so that it may close tightly. A guide ring 26 made of ferromagnetic material is threaded onto the main piston 19 and it guides movement of the sliding pilot piston 9 so that it may seal properly under the force of the pilot return spring 8. Another hole 34 is provided so as to connect all the parts of the back chamber 15 together. One end of the pilot piston 9 is molded with sealing material so as to seize the gas into the back chamber 15 when no power is supplied to the valve construction. A return spring 8 attached to the stop 4 supplies the force necessary to keep the pilot piston 9 closed when no power is supplied to the valve.

[0020] The solenoid valve in accordance with the present invention operates in the following manner.

[0021]FIG. 1 is an axial sectional view through a valve constructed in accordance with this invention. FIG. 1 shows the valve in the “closed” condition. In FIG. 2 the solenoid coil is not energized and the front chamber 25 fills up with high-pressure gas. At the same time, high-pressure gas flows into the back chamber 15 through the gap between the main piston 19 and the spacer 21 and then through a chamber 36 and a small inlet orifice 30. The gases then make its way to the back chamber 15 through the series of orifices and passageways (31, 32, and 33). The orifice 34 is provided so that the entire volume of the back chamber 15 is accessible by the high-pressure gases. At this point, while the coil is not energized, the gas pressure on both sides of the O-ring 17 is equal. In FIG. 4 the solenoid coil has been energized. The pilot piston 9 is attracted by the magnetic force and is pulled toward the stop 4 of core-tube. The gas in the back chamber 15 will subsequently bleed through the drain hole 35 and be released downstream 24 via the network of passageways 27, 23.

[0022] Once the gases in the back chamber 15 are released downstream, the force resulting from the pressure difference between the front 25 and back chamber 15 becomes greater than the force of the return spring 11, which results in the opening of the main piston 19, as shown in FIG. 5. In the meantime, the guide ring 26 is being also attracted by the magnetic force from the stop 4, which keeps the pilot piston 9 from sealing the drain hole 35. This will have the effect of keeping the main piston 19 opened.

[0023] When the solenoid magnetic coil is no longer being energized, the pilot piston seals against the drain hole 35, allowing the pressure between the front 25 and back chambers 15 to equalize again as gas continues to flow into the back chamber 15 through the minuscule inlet hole 30. The main piston 19 is consequently forced by the return spring 11 to close against the seal 20, thus seizing the flow, and the valve returns to the condition shown in FIGS. 1, 2 and 3.

[0024] It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

[0025] While the invention has been illustrated and described as embodied in solenoid gas valve, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

[0026] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:
 1. A solenoid valve, comprising a main body defining a gas inlet passage, a gas outlet passage, and a cavity; a core tube forming a closure for said cavity so as to prevent an escape of gas; a cylindrical main piston slidably movable in said cavity of said main body, said main piston forming a front chamber and a back chamber in said main body, said main piston having a gas conduit for passing the gas from said gas inlet passage to said front chamber and an axial hole for passing the gas from said back chamber into said gas outlet passage with a bleed orifice at one end of said axial hole; said main piston being spring biased to a closed position; a spring biased pilot piston; and electrical coil means associated with said core tube to provide a magnetic field for movements of said pilot piston and said main piston, so that when said coil means is deenergized said pilot piston closes said outlet passage and causes a pressure equalization allowing said return spring to push said main piston to close the valve, while when said coil means is energized said pilot valve opens said outlet passage and lowers a pressure which causes pushing of said main piston to open the valve.
 2. A solenoid valve as defined in claim 1; and further comprising an insert provided in said main piston at one end of said gas conduit and having a minuscule hole for restricting an amount of gas flow into said front chamber, said minuscule hole of said insert having a smaller diameter than a diameter of said bleed hole to provide a pressure difference across both sides of said main piston.
 3. A solenoid valve as defined in claim 1; and further comprising an O-ring located in said main piston for forming said front chamber apart from said gas inlet passage.
 4. A solenoid valve as defined in claim 1, wherein said main piston is provided at one end with a ball seal surface for sealing a main gas flow.
 5. A solenoid valve as defined in claim 4, wherein said main piston has another end with a conical shape providing a seal face with said axial hole in a center.
 6. A solenoid valve as defined in claim 1, wherein said spring means include a guide ring composed of a ferromagnetic material and threaded on said main piston for sliding in a sleeve of said core tube with a minimum gap so as to guide the movement of said main piston or to form a magnetic loop.
 7. A solenoid valve as defined in claim 1; wherein said spring means include a compression spring located inside said core tube to spring-bias said main piston to a closed position.
 8. A solenoid valve as defined in claim 6, wherein said pilot piston is arranged so that it slides smoothly inside said guide ring.
 9. A solenoid valve as defined in claim 1, wherein said spring means include a compression spring arranged in said core tube for pushing said pilot piston against a seal face with an axial hole in a center of said main piston.
 10. A solenoid valve as defined in claim 1; and further comprising a frusto-conical valve seat provided at a bottom end of said cavity, said main piston having a ball seal surface abutting against said seat to close a main gas flow.
 11. A solenoid valve as defined in claim 10; and further comprising an O-ring located in a groove under said valve seat to seal gas around the valve.
 12. A solenoid valve as defined in claim 1, wherein said main piston and said pilot piston are formed so that they act independently, said spring means including two compression springs exerting spring biasing actions of said pistons separately, so that the solenoid valve can not only open rapidly but also close rapidly.
 13. A solenoid valve as defined in claim 1; and further comprising an O-ring element located in a circumferential groove in an outer cylindrical portion of said main piston so as to provide a piston seal between said main piston and a cylindrical seal in said cavity of said body.
 14. A solenoid valve as defined in claim 1, wherein said main piston has a communication conduit hole extending substantially parallel to a central axis of said main piston.
 15. A solenoid valve as defined in claim 14; and further comprising means forming a small cylindrical cavity which connects said communication hole located at an outer circumferential portion of said piston and substantially perpendicular to an axis of said main piston.
 16. A solenoid valve as defined in claim 1, wherein said main piston has one end provided with a conical seal having a central opening connected to a bigger axial hole axially through said main piston so that when the valve is open gas can release to said gas outlet passage.
 17. A solenoid valve as defined in claim 16, wherein said conical seal has a circumferential portion provided with an external thread.
 18. A solenoid valve as defined in claim 16, wherein said main piston has another end provided with a spherical surface, said axial hole extending through a center of said spherical surface.
 19. A solenoid valve as defined in claim 18, wherein said main piston has a recess provided in an outer cylindrical portion adjacent to said spherical surface, said recess allowing gas flow into said cavity of said main body.
 20. A solenoid valve as defined in claim 1; and further comprising a hollow guide ring having an inner thread threaded on said main piston, said guide ring also having a chamber provided on the outer circumferential portion of said guide ring for avoiding blocking of a communication hole.
 21. A solenoid valve as defined in claim 20, wherein said guide ring further has a small hole at a side wall and extending transverse to an axis of said guide ring, to provide communication of gas from outside to an inside chamber of said guide ring.
 22. A solenoid valve as defined in claim 1, wherein said pilot piston has a substantially cylindrical shape and is slidable in an inside chamber of guide ring, one end of said pilot piston being molded with a seal material to the valve with said bleed hole.
 23. A solenoid valve as defined in claim 22, wherein said seal material is a material selected from the group consisting of rubber and plastic. 